Nonradiative DKR processes: revisiting the theory. II. Electron-vibrational mode coupling

TL;DR

This paper revisits the theory of nonradiative decay processes involving electron-vibrational mode coupling, focusing on symmetry-breaking vibrational modes and their effects on electronic state mixing and deexcitation rates.

Contribution

It provides a detailed theoretical analysis of how different vibrational mode couplings influence electronic state mixing and nonradiative decay in F centers.

Findings

Odd-order coupling energies lead to pseudo-Jahn-Teller mixing.

Even-order coupling energies result in pseudo-Renner and dynamic-Renner mixing.

Enhanced mixing widens crossover splitting, increasing nonradiative rates.

Abstract

We summarize a few proposals for mixing F center states through the mediation of an appropriate symmetry-breaking vibrational mode. Electron-mode coupling energies odd-order in the mode coordinates are characteristic of the pseudo-Jahn-Teller mixing of nearly-degenerate opposite-parity electronic states mediated by an odd-parity vibrational mode. Coupling energies even order in the vibrational coordinates lead to a pseudo-Renner mixing of even parity nearly-degenerate states or to dynamic-Renner mixing of degenerate states of whatever symmetry. Both Renner mixing energies add up to widen the crossover splitting of the adiabatic energies thereby enhancing the nonradiative deexcitation rate.